1. Field of the Invention
The present invention relates to engine exhaust systems, and more particularly to exhaust treatment systems that may benefit from the introduction of secondary air.
2. Description of the Related Art
Increasingly strict exhaust emission regulations are requiring better catalysts for use in acoustic mufflers or other exhaust system components, and better performance from existing catalysts. Such catalytic devices often perform significantly better if the gases introduced therein are not solely exhaust gases, but a mixture of exhaust gases and secondary air (generally atmospheric air), allowing the process of catalytic conversion, which may include reduction of nitrogen oxides, oxidation of hydrocarbons, and carbon monoxide, to proceed more efficiently through the chemistry of the gaseous components, as is known.
Existing devices introduce secondary air into the exhaust stream in various ways, using air pumps, control valves, reed valves, and other devices. Such mechanisms are often cumbersome and expensive, and may not allow for the insertion of the proper amount of secondary air. Additionally, existing devices often require the use of baffles and/or other devices to keep acoustic energy from leaving the system through the ports of communication between the secondary air source and the exhaust gases, exceeding noise regulations.
Better and more efficient introduction of secondary air into the exhaust system may result in the use of smaller catalytic devices, since the conversion process will be more efficient. Additionally, even non-catalytic exhaust treatment systems may benefit from the introduction of secondary air to reduce internal exhaust gas and component temperatures.